1. Field of the Invention
The present invention relates to an explosive powder charge-operated setting tool including a housing, a guide cylinder displaceable relative to the housing and having an inner bore, a drive piston displaceably arranged in the inner bore of the guide cylinder, a control pin projecting from the guide cylinder in a direction opposite to the setting direction, a firing pin cooperating with the control pin, a spring for biasing the firing pin in the setting direction, a release pusher formlockingly connectable with the firing pin for displacing the mating surface of the firing pin out of an axial projection surface of the control pin, and a trigger for actuating the release pusher.
2. Description of the Prior Art
For driving nail-shaped fastening elements in a hard constructional component formed of stone, steel, concrete, and the like, explosive powder charge-operated setting tools are used. Such setting tool is produced, e.g., by a company Hilti AG, Liechtenstein, an assignee of the present application. The known setting tool has a housing, a guide cylinder displaceable relative to the housing, and a drive piston displaceably arranged in the inner bore of the guide cylinder. A control pin projects from an end of the guide cylinder facing in a direction opposite to the setting direction. The control pin is displaced, together with the guide cylinder, in the direction opposite to the setting direction when the setting tool is pressed against a constructional component. The control pin cooperates with a mating surface of a firing pin for displacing the firing pin in its firing position. Upon being displaced in its firing position, the firing pin preloads a spring which cooperates with the firing pin and biases the firing pin in the setting direction.
In the firing position of the firing pin, a portion of the firing pin projects into a recess formed in a release pusher which, upon actuation of the trigger, is displaced substantially transverse to the setting direction. Upon the displacement of the release pusher in response to the actuation of trigger, the firing pin rotates about its longitudinal axis, and the mating surface of the firing pin is displaced out of axial projection surface of the control pin. Upon release of the spring preloaded by the firing pin, the spring accelerates the firing pin in the setting discretion until it impacts a firing region of a cartridge and ignites the same. The firing pin is biased sidewise toward the control pin by a return spring. Only upon lifting of the setting tool off the constructional component, the guide cylinder is biased by a corresponding spring into its initial position. The control pin is also displaced in the setting direction, together with the guide cylinder. Already after the displacement of the guide cylinder, in the setting direction, by a distance that corresponds to a length of the axial displacement of the firing pin, the control pin releases the firing pin during the lifting of the setting tool off. As a result, the mating surface of the firing pin can be pivoted by the return spring back into the axial projection of the control pin.
Accordingly, an object of the present invention is to provide an explosive powder charge-operated setting tool in which the release of the firing pin and, thereby, its subsequent displacement into the firing position is prevented upon the contamination of the combustion chamber, which is formed between the bottom of the inner bore of the guide cylinder and the end surface of the drive piston facing in the direction opposite to the setting direction, rising above a predetermined amount.
Another object of the present invention is an explosive powder charge-operated setting tool that can indicate to the operator that a combustion chamber, formed between the inner bore of the guide cylinder and an end surface of the drive piston facing in the direction opposite to the setting direction, has been contaminated above a predetermined amount and that the setting tool requires cleaning.